European Journal of Mechanics B-fluids最新文献_第5页

Multi-scale analysis of solute dispersion in a Casson fluid flow in a tube with wall absorption 管壁吸收卡森流体流动中溶质弥散的多尺度分析

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-22 DOI: 10.1016/j.euromechflu.2025.204419

Aruna A, Radha S, Swarup Barik

The paper presents a two-dimensional concentration distribution of a solute cloud in a non-Newtonian Casson fluid flowing through a tube with an absorbing wall. A multiscale homogenization method is employed to analyze the dispersion, mean, and transverse concentration distributions in both the plug and shear flow regions, which is developed by the yield-stress-driven flow behavior of the Casson fluid. Although most previous studies have primarily focused on determining the dispersion coefficient and mean concentration distribution for non-Newtonian fluids, our study extends this by deriving analytical expressions for the two-dimensional concentration distribution in Casson fluid flows. Numerical simulations are performed to validate the analytical results. The results show that increasing the radius of the plug reduces the dispersion of the solute as a result of suppressed radial mixing within the uniform velocity region. The mean and transverse concentration distributions are strongly influenced by both the plug flow and wall absorption parameters. Although concentration gradients persist longer in the plug region due to the absence of mixing, shear flow accelerates homogenization in the shear region. Stronger wall absorption further restricts transverse mixing, sustaining cross-sectional nonuniformity in both regions. These insights provide a clearer understanding of nutrient and oxygen transport in capillary flows involving non-Newtonian fluids.

本文给出了非牛顿卡森流体流过带吸收壁管时溶质云的二维浓度分布。采用多尺度均质化方法分析了卡森流体屈服应力驱动流动特性所形成的塞流区和剪切流区的弥散分布、平均分布和横向浓度分布。尽管之前的大多数研究主要集中在确定非牛顿流体的分散系数和平均浓度分布，但我们的研究通过推导卡森流体流动中二维浓度分布的解析表达式来扩展这一研究。数值模拟验证了分析结果。结果表明，增大堵头半径可以抑制均匀速度区域内的径向混合，从而降低溶质的分散。平均浓度分布和横向浓度分布受塞流和壁面吸收参数的强烈影响。虽然由于没有混合，堵塞区域的浓度梯度持续时间更长，但剪切流加速了剪切区域的均质化。较强的壁面吸收进一步限制了横向混合，维持了两个区域的截面不均匀性。这些见解提供了一个更清晰的理解营养和氧气运输在毛细管流动涉及非牛顿流体。

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引用次数: 0

Dancing marbles in a soap film 在肥皂片里跳舞的弹珠

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-20 DOI: 10.1016/j.euromechflu.2025.204423

Youna Louyer , Benjamin Dollet , Isabelle Cantat , Anaïs Gauthier

Two millimeter-sized particles deposited in a large horizontal soap film are attracted towards each other. Due to the very low friction at the surface of the soap film, the particles can exhibit a complex trajectory, and appear to dance together for about ten seconds before colliding. We give here a short overview of the topic and its perspectives.

两毫米大小的颗粒沉积在一个大的水平肥皂膜上，相互吸引。由于肥皂膜表面的摩擦力非常小，这些粒子可以呈现出复杂的轨迹，在碰撞前似乎会一起跳舞大约十秒钟。我们在这里对这个主题及其观点做一个简短的概述。

引用次数: 0

Differential equation based wall distance approaches for maritime engineering flows 基于微分方程的船舶工程流壁距方法

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-20 DOI: 10.1016/j.euromechflu.2025.204418

Niklas Kühl

This study investigates differential-equation-based formulations for computing wall-distance functions in Computational Fluid Dynamics (CFD). The wall distance directly influences turbulence modeling by controlling near-wall damping functions and blending behavior, and is particularly critical for industrial applications, for example in maritime contexts involving complex ship geometries and flow configurations. Several approaches are compared, including linear and nonlinear p-Poisson, Screened-Poisson, Eikonal, regularized Eikonal/Hamilton–Jacobi, and Laplace methods. Each formulation is discretized and assessed for numerical stability, efficiency, and accuracy against an exact geometric benchmark.

The validated models are applied to hydrodynamic and aerodynamic ship flows. For a model-scale bulk carrier (

R e_{L} = 7.2 \times 1 0^{6}

,

F n = 0.142

), Reynolds-Averaged Navier–Stokes (RANS) simulations with Shear Stress Transport (SST) turbulence show that different wall-distance formulations alter resistance, trim, and sinkage by less than 0.1%. A temporally constant wall-distance field proves sufficient for accurate propulsion predictions. In contrast, a full-scale feeder ship (

R e_{L} = 5.0 \times 1 0^{8}

) analyzed with a hybrid RANS/LES (IDDES) model exhibits greater sensitivity to wall-distance definitions.

Among the tested methods, the convective Eikonal or Hamilton–Jacobi formulations with deferred correction achieve the best compromise between robustness, computational cost, and accuracy, whereas p-Poisson and Screened-Poisson variants are more parameter-sensitive and computationally expensive.

本文研究了计算流体力学（CFD）中基于微分方程的壁距函数计算公式。壁距通过控制近壁阻尼函数和混合行为直接影响湍流建模，对于工业应用尤其重要，例如在涉及复杂船舶几何形状和流动配置的海事环境中。比较了几种方法，包括线性和非线性p-泊松方法、筛选-泊松方法、Eikonal方法、正则化Eikonal/ Hamilton-Jacobi方法和拉普拉斯方法。每个公式是离散和评估的数值稳定性，效率和精度对一个精确的几何基准。验证的模型应用于船舶的水动力和气动流动。对于模型级散货船（ReL=7.2×106, Fn=0.142），具有剪切应力输运（SST）湍流的reynolds - average Navier-Stokes （RANS）模拟表明，不同的壁距配方对阻力、纵倾和沉差的影响小于0.1%。一个时间上恒定的壁距场足以进行精确的推进预测。相比之下，使用混合RANS/LES （IDDES）模型分析的全尺寸支线船（ReL=5.0×108）对壁距定义表现出更大的敏感性。在测试的方法中，延迟校正的对流Eikonal或Hamilton-Jacobi公式在鲁棒性、计算成本和准确性之间取得了最佳折衷，而p-Poisson和Screened-Poisson变体对参数更敏感，计算成本更高。

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引用次数: 0

An improved SPH method for simulating near-surface underwater explosions in shallow water 模拟浅水近水面水下爆炸的改进SPH方法

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-19 DOI: 10.1016/j.euromechflu.2025.204420

Lingyun Tian, Xiaoyang Xu

Near-surface underwater explosions in shallow water involve complex interactions among shock waves, free surfaces, and bottom boundaries, which significantly affect shock wave propagation and pressure distribution. These interactions pose challenges for damage assessment of marine and coastal structures. In this study, an improved smoothed particle hydrodynamics (SPH) method is developed to simulate near-surface underwater explosions in shallow water. The improvements include a density-continuity-based discretization, artificial viscosity, variable smoothing length, and a particle shifting technique, which mitigate tensile instability in the thin water layer near the free surface and enhance the accuracy of underwater explosion simulations. First, the proposed SPH method is applied to simulate TNT slab detonation and free-field underwater explosions. The effectiveness of the proposed method is validated by comparing simulation results with theoretical solutions. Then, an SPH model is developed to investigate shock wave evolution under the impact of surface boundary conditions in near-surface underwater explosions. Finally, the method is extended to simulate near-surface underwater explosions in shallow water, investigating the effects of bottom boundary inclination on shock wave reflection and bubble morphology. The results reveal that shallow charge depths enhance surface disturbances, while sloped boundaries induce asymmetric pressure focusing and bubble deformation. Overall, the improved SPH method demonstrates reliable capability in capturing shock wave propagation, reflection, surface disturbance, and bubble expansion in near-surface underwater explosions.

浅水近水面水下爆炸涉及激波、自由面和底边界之间复杂的相互作用，对激波传播和压力分布有重要影响。这些相互作用对海洋和海岸结构物的损害评估提出了挑战。本文提出了一种改进的光滑粒子流体力学（SPH）方法，用于模拟浅水近水面水下爆炸。这些改进包括基于密度连续性的离散化、人工黏度、可变平滑长度和粒子移动技术，这些改进减轻了靠近自由表面的薄水层的拉伸不稳定性，提高了水下爆炸模拟的准确性。首先，将所提出的SPH方法应用于TNT板坯爆轰和自由场水下爆炸模拟。通过仿真结果与理论解的比较，验证了该方法的有效性。在此基础上，建立了近水面水下爆炸的SPH模型，研究了在表面边界条件影响下的冲击波演化。最后，将该方法推广到浅水近水面水下爆炸模拟中，研究了底边界倾角对激波反射和气泡形态的影响。结果表明，较浅的装药深度增强了表面扰动，而倾斜的边界引起了不对称的压力聚焦和气泡变形。总的来说，改进的SPH方法在捕获近水面水下爆炸中的激波传播、反射、表面扰动和气泡膨胀方面表现出可靠的能力。

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引用次数: 0

Oscillatory Stokes flow past a slip–stick Janus sphere 振荡斯托克斯流经过一个滑杆Janus球

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-19 DOI: 10.1016/j.euromechflu.2025.204421

Dadi Dimple S.S., B. Sri Padmavati

We consider a translating and rotating spherical slip–stick Janus particle of unit radius in an oscillatory Stokes flow. Janus particles are unique microparticles with surfaces that exhibit two or more different physical properties in different regions owing to different surface roughness in these regions. Here we assume that the sphere’s surface consists of two different regions characterized by different slip parameters in each region. We give a method of solution and elucidate it with different configurations of such regions illustrated by a sphere enveloped by (i) a cap, (ii) a horizontal strip, and (iii) a patch. We study the effect of such a heterogeneous nature of the surface on some physical properties, such as drag and torque experienced by the sphere. We also observe the effect of non-uniform surface roughness on the translational and rotational velocity of the particle.

考虑振荡斯托克斯流中一个单位半径的平动旋转球形滑棒Janus粒子。两面粒子是一种独特的微粒，由于不同区域的表面粗糙度不同，其表面在不同区域表现出两种或两种以上不同的物理性质。这里我们假设球体表面由两个不同的区域组成，每个区域的滑动参数不同。我们给出了一种解的方法，并用由(i)帽，（ii）水平线和（iii）斑块包裹的球体所表示的这些区域的不同构型来说明它。我们研究了表面的这种非均质性对某些物理性质的影响，如球体所经历的阻力和扭矩。我们还观察了非均匀表面粗糙度对粒子平动和旋转速度的影响。

引用次数: 0

Machine learning based flow simulator: Flow around an airfoil with vortex generators 机器学习为基础的流动模拟器：流动周围的翼型与涡发生器

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-19 DOI: 10.1016/j.euromechflu.2025.204417

Muharrem Hilmi Aksoy , Murat Ispir , Mahdi Tabatabaei Malazi , Abdulkerim Okbaz

Controlling the flow structure around an airfoil is crucial for increasing lift and reducing drag. Delaying flow separation improves aerodynamic performance, especially in aircraft and wind turbines. In recent years, artificial intelligence and machine learning methods have emerged as fast and cost-effective alternatives to traditional approaches in fluid mechanics. In this study, we aimed to control the flow around the NACA (National Advisory Committee for Aeronautics) 4412 airfoil using vortex generators (VGs) and to develop a machine-learning-based flow simulator that predicts velocity components based on angle of attack, VG yaw angle, and spatial coordinates. Experimental measurements were conducted in an open-surface, closed-loop water channel at a Reynolds number of Re = 1.0 × 10⁴ using a two-dimensional Particle Image Velocimetry (PIV) system. A total of 60,500 data points were collected per velocity component from 20 experimental cases within the range of α = 0°–20° and β = 15°–30°. A Multilayer Perceptron (MLP) model implemented using TensorFlow was trained to predict the ensemble-averaged 〈u〉 and 〈v〉 velocity components. We analyzed the effects of hidden layer neuron count and mini-batch size, achieving the highest accuracy with 41 neurons and a batch size of 4, yielding R² values of 0.978 for 〈u〉 and 0.950 for 〈v〉. The error distributions were symmetric and closely approximated a Gaussian distribution. Experimental results showed that VGs delayed early-stage flow separation at low α but became less effective at higher α. The MLP model successfully reconstructed major flow features, providing a reliable data-driven alternative to CFD-based methods. Future work will extend the model to various airfoils, VG designs, Reynolds numbers, and unsteady flows using time-resolved PIV data.

控制翼型周围的流动结构是增加升力和减少阻力的关键。延迟流动分离可以改善空气动力学性能，特别是在飞机和风力涡轮机中。近年来，人工智能和机器学习方法已经成为流体力学中传统方法的快速和经济的替代品。在这项研究中，我们的目标是使用涡发生器（VG）控制NACA（美国国家航空咨询委员会）4412翼型周围的流动，并开发一个基于机器学习的流动模拟器，该模拟器可以根据迎角、VG偏航角和空间坐标来预测速度分量。实验测量采用二维粒子图像测速（PIV）系统，在雷诺数Re = 1.0 × 10⁴的开表面闭环水道中进行。在α = 0°-20°和β = 15°-30°范围内的20个实验案例中，每个速度分量共收集了60500个数据点。使用TensorFlow实现的多层感知器（MLP）模型被训练来预测集合平均< u >和< v >速度分量。我们分析了隐藏层神经元数量和小批大小的影响，在41个神经元和4个批大小的情况下获得了最高的准确性，< u >和< v >的R²值分别为0.978和0.950。误差分布是对称的，近似于高斯分布。实验结果表明，在低α条件下，VGs延迟了早期的流动分离，而在高α条件下，VGs的作用减弱。MLP模型成功地重建了主要的流体特征，为基于cfd的方法提供了可靠的数据驱动替代方案。未来的工作将扩展模型到各种翼型，VG设计，雷诺数，和非定常流动使用时间分辨PIV数据。

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引用次数: 0

Effect of momentum flux ratio on the flow and combustion behavior of coaxial jets with annular blockage 动量通量比对环形阻塞同轴射流流动和燃烧特性的影响

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-14 DOI: 10.1016/j.euromechflu.2025.204415

Shiferaw Regassa Jufar , Minh Duc Le

The flow and combustion characteristics of coaxial jets with annular blockage have been studied numerically. The model was validated with experimental results from related studies. Based on the observations presented in the study, two dominant flow regimes were identified as the momentum flux ratio varied. These regimes can be classified as either central or annular jet-dominated, based on the nature of the vortical structures and stagnation points in the flow field. The central jet-dominated flow occurs at momentum flux ratios below 0.25, where entrainment in the inner mixing region plays a key role. In contrast, the annular jet-dominated flow, which occurs at momentum flux ratios above 2.5, enhances mixing through the recirculation of streams within the counter-rotating vortex rings. In combustion, low momentum flux ratios result in longer flame lengths due to the absence of stagnation points and counter-rotating vortex rings, which lead to poor mixing performance. At higher momentum flux ratios, the formation of counter-rotating vortex rings and the stagnation points enhance mixing, resulting in shorter flame lengths and improved combustion performance. The novelty of this study lies in defining the characteristic flow regimes based on the Reynolds numbers of the annular and central jets, which helps distinguish the dominant flow modes. For a given Reynolds number of the jets, the prevailing mode can be identified to optimize both mixing and combustion performance.

用数值方法研究了带环形阻塞的同轴射流的流动和燃烧特性。用相关研究的实验结果对模型进行了验证。根据研究中提出的观察，确定了动量通量比变化时的两种主要流动形式。根据流场中旋涡结构和滞止点的性质，这些状态可以分为中心型和环状型两种。在动量通量比小于0.25时，中心射流占主导地位，内部混合区的夹带起关键作用。相反，在动量通量比大于2.5时，环形射流主导的流动通过在反向旋转的涡旋环内的流的再循环增强了混合。在燃烧过程中，动量通量比较低，由于没有停滞点和反向旋转的涡流环，导致火焰长度较长，导致混合性能较差。在较高的动量通量比下，反向旋转涡环和驻点的形成增强了混合，从而缩短了火焰长度，改善了燃烧性能。本研究的新颖之处在于基于环形和中心射流的雷诺数定义了特征流型，这有助于区分主要的流动模式。对于给定的射流雷诺数，可以识别主导模式，以优化混合和燃烧性能。

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引用次数: 0

Bound states for a quasigeostrophic two-layer model in a baroclinic shear flow 斜压切变流中准等转两层模型的束缚态

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-12 DOI: 10.1016/j.euromechflu.2025.204403

Xi-Hu Wu , Yuan Shen

In geophysical hydrodynamics, baroclinic instability refers to the process in which the perturbations absorb energy from potential energy of the mean flow. In this manuscript, we focus our attention on a nonlinear system modeling the propagation of the wave packet within a quasigeostrophic two-layer model in a baroclinic shear flow. With the aid of the generalized Darboux transformation method, we derive several types of the semi-rational solutions to explore bound states among the localized waves and multi-pole localized waves. On different backgrounds, the wave packet and the wave-induced modification of the basic flow manifest themselves as the bound states among multiple solitons/breathers, the bound states among a single soliton/breather component and the multi-pole solitons/breathers, and the bound states among two sets of the double-pole solitons. Physical dynamics of those bound-state nonlinear waves are discussed. We find that the bound states among the solitons/breathers exhibit periodic attractions or repulsions, while the bound states among the solitons/breathers and multi-pole solitons/breathers exhibit non-periodic interactions. This work may provide theoretical support and explanations for the complex and variable natural mechanisms underlying baroclinic instability.

在地球物理流体力学中，斜压不稳定是指扰动从平均流的势能中吸收能量的过程。在本文中，我们将注意力集中在一个非线性系统中，模拟了斜压切变流中准等转两层模型中波包的传播。利用广义Darboux变换方法，导出了几种类型的半有理解，用于探索局域波和多极局域波之间的界态。在不同的背景下，基本流的波包和波致修正表现为多个孤子/呼吸子之间的束缚态、单个孤子/呼吸子与多极孤子/呼吸子之间的束缚态以及两组双极孤子之间的束缚态。讨论了这些束缚态非线性波的物理动力学。我们发现孤子/呼吸子之间的束缚态表现出周期性的吸引或排斥，而孤子/呼吸子和多极孤子/呼吸子之间的束缚态表现出非周期性的相互作用。本研究为斜压不稳定复杂多变的自然机制提供了理论支持和解释。

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引用次数: 0

Electrokinetic ion transport of non-Newtonian fluids in a bipolar nanochannel 双极纳米通道中非牛顿流体的电动力学离子输运

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-12 DOI: 10.1016/j.euromechflu.2025.204416

Jie Li, Li Peng, Yu Hao

Precise regulation of ion transport in nanofluidics demonstrates great application prospects in the field of ion separation and pre-enrichment. Compared with unipolar nanochannels, bipolar nanochannels show superior performance in ion transport control and can achieve higher ion enrichment ratio and ion interception efficiency. Beyond these fundamental advantages, such nanofluidics gain additional relevance from the widespread use of non-Newtonian fluids across biomedical and chemical applications. This research explores a novel approach—converting a unipolar nanochannel into a bipolar configuration by integrating a gated structure at its center and utilizing a positively charged surface. The Navier-Stokes equations model fluid dynamics, while the Poisson-Nernst-Planck formulation depicts electric potential and ion concentration profiles. Through numerical simulations, the electrokinetic transport behavior of power-law fluids within the bipolar nanochannel is analyzed. The findings indicate that for the fluid characterized by a power-law index of n = 0.95, a rise in gate surface charge density from 0 to 25 mC/m² leads to a roughly 25 % boost in ionic current. However, this increase comes at a cost—the ion selectivity coefficient drops sharply by 46 %. Furthermore, at gate densities of 0 and 40 mC/m², the power-law index rises from 0.95 to 1.05, with the ionic current climbing about 31 % and 4 % accordingly.

纳米流体中离子输运的精确调控在离子分离和预富集领域具有广阔的应用前景。与单极纳米通道相比，双极纳米通道具有更好的离子输运控制性能，可以实现更高的离子富集率和离子拦截效率。除了这些基本优势之外，这种纳米流体还因非牛顿流体在生物医学和化学应用中的广泛应用而获得了额外的相关性。本研究探索了一种新颖的方法，通过在其中心集成门控结构并利用带正电的表面将单极纳米通道转换为双极结构。Navier-Stokes方程模拟流体动力学，而泊松-能斯特-普朗克公式描述电势和离子浓度分布。通过数值模拟，分析了幂律流体在双极纳米通道内的电动力学输运行为。研究结果表明，对于幂律指数为n = 0.95的流体，栅极表面电荷密度从0增加到25 mC/m2，导致离子电流增加约25 %。然而，这种增加是有代价的——离子选择系数急剧下降了46% %。在栅极密度为0和40 mC/m2时，幂律指数从0.95上升到1.05，离子电流相应上升约31% %和4% %。

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引用次数: 0

Development of aeroacoustic control devices for a square cylinder using adjoint lattice Boltzmann method 用伴随晶格玻尔兹曼方法研制方形圆柱体气动声控制装置

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-08 DOI: 10.1016/j.euromechflu.2025.204413

Kazuya Kusano

The control of aerodynamic noise is essential in various fields, including mechanical and aerospace engineering applications such as pantographs of high-speed trains and aircraft landing gears. Traditional devices, such as splitter plates, have long been employed to suppress wake flows and the resulting noise; however, the development of novel devices that outperform these classical designs has yet to be achieved. The present study seeked to develop innovative control devices using an aeroacoustic optimization framework that integrates the lattice Boltzmann method (LBM) with the adjoint method to modify the rear surface of a square cylinder. The Reynolds number was set to 150 for a two-dimensional laminar flow, and the Mach number was set to 0.2. The optimization created a ridge shape near the rear edge. Flow and acoustic analyses using the LBM showed that this shape successfully suppressed wake flow oscillations and mitigated the generation of aeolian tones. Additionally, a new passive control technique, namely, the installation of tapered splitter plates near the rear edge of the square cylinder, was proposed by simplifying the optimized shape. The LBM simulations demonstrated that the tapered splitter plates outperformed the conventional straight splitter plates in controlling the wake flow and flow-induced sound of the square cylinder.

气动噪声的控制在各个领域都是必不可少的，包括机械和航空航天工程应用，如高速列车和飞机起落架的受电弓。传统的装置，如分流板，长期以来一直被用来抑制尾流和由此产生的噪音；然而，超越这些经典设计的新型设备的开发尚未实现。本研究旨在利用结合晶格玻尔兹曼方法（LBM）和伴随方法的气动声学优化框架来开发创新的控制装置，以修改方形圆柱体的后表面。二维层流的雷诺数设为150，马赫数设为0.2。优化创造了一个山脊形状附近的后边缘。利用LBM进行的流动和声学分析表明，这种形状成功地抑制了尾流振荡，减轻了风成调的产生。此外，通过简化优化形状，提出了一种新的被动控制技术，即在方柱体后缘附近安装锥形分流板。LBM仿真结果表明，锥形分流板对方形圆柱尾流和流声的控制效果优于传统的直线分流板。

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引用次数: 0